<div id="map"></div>
<script>
    var map = new mapboxgl.Map({
        container: 'map',
        style: 'mapbox://styles/mapbox/light-v10',
        zoom: 13,
        center: [-122.447303, 37.753574]
    });

    map.on('load', function() {
        map.addSource('mapbox-terrain', {
            type: 'vector',
            url: 'mapbox://mapbox.mapbox-terrain-v2'
        });
        map.addLayer({
            'id': 'terrain-data',
            'type': 'line',
            'source': 'mapbox-terrain',
            'source-layer': 'contour',
            'layout': {
                'line-join': 'round',
                'line-cap': 'round'
            },
            'paint': {
                'line-color': '#ff69b4',
                'line-width': 1
            }
        });
    });
</script>
